Abstract
Object-based attention (OBA) leads to preferential processing of visual information within the boundaries of an attended object. Pilz et al. (2012) demonstrated that this preferential processing was larger for horizontally-oriented rectangles than for vertically-oriented rectangles. However, Greenberg et al. (VSS, 2014) showed that, when controlling for shifts of attention across the vertical meridian of the visual field (thereby eliminating attention shifts across this axis), effects of object orientation are eliminated, suggesting that object orientation may not affect OBA. These studies used the double-rectangle cueing paradigm (Egly et al., 1994) in which attention shifts between objects are contrasted against shifts within objects. Our goal here was to examine the distribution of solely within-object shifts across the meridians. Eighteen participants viewed an object consisting of a vertical rectangle and a horizontal rectangle joined to form a unified object in the shape of a right angle. While subjects fixated centrally, the object vertex was randomly positioned in one screen quadrant on each trial such that one object component always crossed the vertical meridian and the other always crossed the horizontal meridian. Following a peripheral cue at the object vertex, the target appeared at the cued location (“valid”), or at one of two locations equidistant from the cue - the uncued location of the horizontal component (“invalid-horizontal”) or the uncued location of the vertical component (“invalid-vertical”). Results showed that participants were faster to detect valid targets compared to invalid targets. Furthermore, RTs varied by target hemifield, regardless of cue location. However, contrary to our hypothesis, participants were faster for invalid-horizontal locations than for invalid-vertical locations, suggesting that OBA is distributed more efficiently along the horizontal meridian than the vertical meridian. Thus, OBA may be allocated unevenly within objects that cross the vertical versus horizontal meridian of the visual field.
Meeting abstract presented at VSS 2015